1. Field of the Invention
The present invention generally relates to a circuit device having an inductor and a capacitor in parallel connection and the application thereof.
2. Description of Related Art
Along with the development tendency of electronic products that the light, slim, short and small requirements and the integration of multi functions, more and more circuit devices need to be integrated into a semiconductor chip. The inductance coupling device herein is one of indispensable devices in designing a semiconductor chip. The inductance coupling device is broadly used in various applications, which include a signal-converting mechanism application in numerous circuits or a cavity resonator coupling application in passive devices.
Taking a radio-frequency front stage circuit (RF front stage circuit) in a communication system as an example, a filter often plays an indispensable role, and the inductance coupling device is serving as a familiar and important component in a filter. Usually, the filter is laid out at the front-most stage of a system and in charge of allowing a signal with an operation bandwidth to pass the filter and blocking signals with other bandwidths. In terms of the said system, the signals with other bandwidths are considered as noise, which would quite affect the communication quality of the system.
In terms of a planar circuit with, for example, a microstrip-line environment or a strip-line environment, many ways exist to design a filter. Once the filter device needs to be integrated into a chip, considering the limitation of chip area, the filter can not be designed by using a quarter-wave coaxial cavity resonator architecture which is very common one in a planar circuit. Instead, the filter can be implemented by using LC architecture only, wherein the capacitor and the inductor are embedded in a chip.
In a filter design, for example, a resonance structure with an inductor and a capacitor in parallel connection is well known as a basic and important component. In a common chip design however, only a limited and unchanged number of inductors and capacitors embedded in a chip are allowed for designing the circuit; in addition, transmission lines are used to connect each independent inductor or capacitor so as to finish a required structure design. In comparison with the required design area of a capacitor, the area of an inductor is quite larger. To adapt the above-mentioned circumstance, additional connection lines are required for a resonance structure with an inductor and a capacitor in parallel connection, which not only increases the required area of the designed filter, but also brings an additional connection line effect. A designer must consider about it. Therefore, if the additional connection circuits can be reduced, the resonance structure with an inductor and a capacitor in parallel connection at least benefits the chip design with an embedded filter.